“I woke up this mornin’ and all my shrimps was dead and gone” is a line sung by the legendary blues artist Robert Johnson back in 1937. It’s a line that sadly resonates today according to new research led by the Oxford University Museum of Natural History and the International Union for Conservation of Nature (IUCN), recently published in the journal PLOSONE. Researchers found that almost a third of freshwater shrimp species, a group which support the livelihoods of some of the world’s poorest communities, are threatened with extinction.

Over the past three years the team – including researchers from the UK, Australia, Austria, Brazil, Indonesia, Mexico, Singapore and Taiwan – assessed the risk of extinction for the world’s 763 freshwater shrimp species using the IUCN Red List Categories and Criteria. They found that 27.8% of species faced pressures severe enough to classify them as ‘threatened’. These included urban and agricultural pollution, human intrusions and disturbance particularly impacting cave dwelling species, invasive species, dams and water abstraction, and impacts from mining. Of unique significance amongst freshwater invertebrates is collecting of wild populations for the ornamental aquarium trade, which is a significant threat to the colourful species found in the ancient lakes of Sulawesi.

“Freshwater shrimps are extensively harvested for human food, especially by the poorest communities in tropical regions, where they often dominate the biomass of streams playing a key role in regulating many ecosystem functions. However, little is known about the impacts the loss of these species may cause to ecosystem services. ” Sammy De Grave, lead author, Oxford University Museum of Natural History

Caridina woltereckae, endemic to Lake Towuti (Sulawesi), currently under threat due to overharvesting for the aquarium trade, pollution and invasive fish species (Image: C Lukhaup)

Two species were declared as “Extinct” and a further ten are also “Possibly Extinct”, but require field surveys to confirm that status. Several of these species are only known from a single cave or stream which have undergone significant levels of habitat degradation and conversion, and have not been sighted for decades. For example, Macrobrachium purpureamanus is only known from peat swamps on Kundur Island, Riau Archipelago (Indonesia), an area which has been extensively converted to an oil palm plantation since 1988.

The research, which collated distribution data for all species, identified areas containing high levels of species diversity in the Western Ghats, Madagascar, the Guyana Shield area, the upper Amazon, Sulawesi and Indo-China. Additionally, high concentrations of cave dwelling species were found in karst rich areas in China, the western Balkan Peninsula, the Philippines and Cuba.

Global species richness of freshwater shrimps

Although threatened shrimp species are found across the globe, notable concentrations were found in Sulawesi (Indonesia), Cuba, the Philippines and southern China, many of which are restricted to cave habitats. In addition to cave dwelling species, those restricted to lakes, and freshwater springs also face higher levels of threat. For example, the Alabama Cave Shrimp (Palaemonias alabamae) is an Endangered species, known from only four cave systems in Alabama (USA) currently under threat from groundwater abstraction and habitat change.

Palaemonias alabamae (Image: D Fenolio)

“The high levels of extinction threat that the team found for freshwater shrimps have also been found for freshwater crabs and crayfish, and these studies of global faunas highlight the fragile state of freshwater invertebrates across the world. Sadly, the prospect of losing these important species often goes unnoticed. The information on these threatened freshwater crustaceans is readily available on the IUCN Red List and needs to be incorporated into decision making at all levels if we are to protect the world’s rapidly deteriorating freshwater habitats and the amazing but highly threatened species that live there.” Neil Cumberlidge, Chair of the IUCN Freshwater Crustacean Specialist Group

However, for 37% of species there was not sufficient information to identify if they were threatened or not, and these were classed as “Data Deficient”. This deficiency was particularly acute in China and Africa, which both hold significant levels of biodiversity and therefore the current number of species assessed as threatened is very likely an underestimation.

The key conservation recommendations resulting from the study include the need to adopt integrated water resource management (IWRM) principles, environmental flow concepts and comprehensive environmental and social impact assessments (EISAs) to ensure that freshwater biodiversity is incorporated into the decision making processes that affect freshwater systems. In addition, there is an urgent need for field research to help us better understand the life histories, threats and distribution of many shrimp species, particularly those species that migrate to marine or brackish environments for larval development.

Werner Klotz, one of the co-authors of the study, collecting a new species of freshwater shrimp in Taiwan.

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